Regenerative telegraph repeater



March 5, 1935.

T. A. McCANN REGENERATIVE TELEGRAPH REPEATER Filed April 20, 1953 LOOP EAST r EU? LOOP WEST INVENTOR. 7'. A. Mc CANN A TTO/PNE) Patented Mar. 5, 1935 UNITED STATES REGENERATIVE TELEGRAPH REPEATER Thomas Addison 'McGan'n, East Orange, N. J., assignor to American Telephone and Telegraph Company, a corporation of New York Application April 20, 1933, Serial No. 667,123

4 Claims.

This invention relates to regenerative telegraph repeaters and particularly to telegraph repeaters of the start-stop type.

An object of the invention is to regenerate into substantially their original form signals which have become distorted in transmission so that they may be subjected to distortion due to subsequent transmission without losing their identity.

A further object of the invention is to simplify the operation and reduce the required maintenance of regenerative repeaters of this type.

The invention is in the nature of an improvement on the regenerative telegraph repeater disclosed in Patent No; 1,771,453, issued to G. S. Vernam on July 29, 1930. In accordance with that disclosure the telegraph repeater is provided with a start-stop distributor for each. direction of transmission; each distributor has a set of retransmitting contacts for transferring impulses from the receiving relay to the retransmitting relay and a set of locking contacts for locking of the receiving relay by means of its biasing winding during the greater part of each received impulse.

In accordance with the present invention, a telegraph repeater of this type is arranged so that the distributor or timing mechanism requires'only a single set of interrupter contacts, whereby contact trouble is reduced.

The retransmitting and locking circuits are combined in such a manner that they may be controlled by only a single set ,of distributor contacts, and more particularly the biasing winding of the receiving relay and the operating winding of the retransmitting or sending relay are connected in parallel circuits extending through the single contact set of the distributor to the contacts of the receiving relay, and the biasing winding serves the double purpose of self-locking during each impulse received by the relay and of holding the relay against operation during transmission into the line circuit which includes its operating winding.

General description of apparatus A regenerative repeater system in accordance with this invention for repeating signals in either direction between two line sections, one of which, for convenience, is called loop east and the other loop west, is illustrated in Fig. 1 of the drawing.

In Fig. 2 is shown diagrammatically an example of a series of impulses which constitute a character code and which arrive at the repeater station without distortion;

Fig. 3 shows the same series of impulses received at the repeater station in a distorted form.

As shown in Fig. 1 the system comprises two distributor faces, one for repeating from west to east and the other for repeating from east to west. Each face comprises a set of contact rings associated with which is a brush or wiper SB, adapted to be moved over the distributor face in isochronism with series of received signals by'a motor, which is not shown. In practice, the rings are circular and the brush sweeps over the seven segments in one revolution when the. catch 1'7 is released by start magnet 16. Associated with each distributor are a locking relay, a retransmitting or sending relay, and a receiving relay, the relays associated with the loop west being identified as WLR, WSR and WRR, respectively,

and those with the loop east ELR, ESR and ERR, respectively. The function of these relays will be made clearbythe following detailed description of the operation of the system in repeating signals from the loop west into the loop east.

Detailed descriptionof operation In systems of the type described the line circuit, or loop as it is termed, is normally closedv through a source of current. Thus, referring to the drawing, the loop west is normally closed through a source of current at the distant end, the lower or operating winding of the west receiving relay WRR and the armature and contact of the west sending relay WSR..' For the purpose of explanation it is assumed that an electron flow from left to right through any relay winding, as it is shown in the drawing, urges the relay armature from left to right, and vice versa when the electron flow is in the opposite direction. The direction of the electron flow from the source at the distant end of the loop west is always from right to left through the relay WRR, as indicated by the arrow. Thus the armature of this relay is held on its marking contact by a loop current, which may conveniently be made approximately 60 milliamperes. An opposing current of approximately milliam peres flows through the upper winding, which will hereinafter be termed the biasing winding. The circuit for the 30 milliampere current ex: tends from positive battery over the contact and armature of the west locking relay -WLR through high resistance 13 and the biasing winding of the 'west receiving relay to ground. This biasing current, which is made about 30 milliamperes by adjustment of resistance 13, tends to move the receiving relay armature to its spacing contact. 7

A locking circuit for the west sending relay WSR I and the west locking relay ,WLR is also closed at the marking contact of relay 'WLR. and extends through resistance 11 and the upper windings in series of relays WLR and WSR to ground. The locking current in this circuit is conveniently made about 30 milliamperes and serves to hold these relays firmly against the contacts in either operated position while the operating windings are deenergized.

When all the relays are in their idle condition (on their marking contacts) the start magnet circuit for the west to'east distributor is short- 7 circuited. This circuit extends through the stop position of the distributor as follows: from negative battery through the marking contact and armature of the west receiving relay WRR, over the common ring 18, brush SB, stop segment SS of the distributor, through the start magnet 16 and back to negative battery over the armature and marking contact of the east locking relay ELR.

Repeating signals from west to east In start-stop telegraph systems seven impulses are usually transmitted for each si nal character. These comprise an initial or starting impulse, which is commonly a spacing impulse, followed by five character impulses which may be either marking or spacing represent the signal character to be transmitted. These are followed by a last or stop impulse which is a marking impulse and stops the distributor. For purposes of explanation it will be assumed that an F signal is to be repeated from the loop west into the loop east. The seven impulses of an F signal are the start, which is spacing, #1 marking, #2 spacing, #3 and #4 marking, #5 spacing and the stop impulse, which is marking. Such :a series of impulses is graphically represented in Fig. 2, the marking impulses being represented by values above the zero line and the spacing impulses as zero values of current. Thus the loop is normally closed, but changes to open .or spacing condition at time A at which the start impulse arrives.

This start 'or open impulse removes the 60 milliampere current from the operating winding of the west receiving relay WEB and permits the 30 milliampere biasing current in the upper winding to move the armature to the spacing contact. This applies positive battery to one end of the start magnet circuit and current flows from positive battery at the spacing contact of the west receiving relay WRR over the common ring 18, brush SB and stop segment SS ofthe distributor, through the start magnet 16 to negative battery at the marking contact of the east locking relay ELR. Start magnet 16 thereupon operates to raise the stop latch l'i'and release the brush arm carrying the brush SB.

Almost immediately after leaving the stop ment, the brush SB contacts with sending ment #7, which applies positive battery from the spacing contact of relay WRR, over the common ring 18, brush SB, and segment #7 through re-. sistances 22 and 23 and the upper or'cperating windings of the east locking relay ELR and the east sending relay ESE to ground; the current in this operating circuit is conveniently made to be about milliamperes. An electron flow from right to left therefore occurs through the upper windings of these two relays which is strong enough to overcome the .30 milliampere locking current through the lower windings andmove the armatures to their spacing contacts, thus segseg-

opening the loop east at the east sending relay contacts and retransmitting the start impulse over the loop east. These relays are now locked on their spacing contacts by current from positive battery over the armature of the east locking relay ELR, through resistance 25 and the lower or locking windings of the relays ELR and ESR to ground. Theoperation oi relay ELR reverses the direction of the biasing current through resistance 27 and the biasing winding of the east receiving relay ERR, so that it now is in such a direction as to hold the armature of the relay ERR on the marking contact while the loop east is open at the contacts of the east sending relay. At this time the start magnet is deenergized, since its circuit has been opened by the brush SB passing ofi the stop segment Sin ultaneously'with the closing on segment #7 of the operating circuit for relays ELR and ESR a locking circuit is closed on segment #7 for the west receiving relay, which may be traced from positive battery at the spacing contact of relay WR-R over ring 18, brush SB and segment #7, through low resistance 14 and. the biasing winding of relay WRR. The current in this circuit is made about so millianiperes by adjustment resistance 14. and isin such a'direction as to aid the biasing current in holding the armature of relay WRR against the spacing contact. Thus the relay is locked against operation while the brush SE is passin over segment #7, since the combined currents amount to about milliamperes and thus are suficient to overpower a marking impulse of 60 milliamperes through the operating winding; this provision insures the completion of the operation and the locking of relays ELR, ESR and ERR just described. Thus a premature change-in the west loop of the condition which brought about these operations will not interfere with their completion. However, as soon as brush SB leaves ..-e #5. the locking circuit for relay WPUPu on and the relay is free to respond to a new impute r nile the brush SB passes from segment #7 to segment #1.

The brush traverses the segment in the oiT-stop positions in approximate synchronism with the signal impulses from the loop west, so that by the time the brush SB reaches the #1 segment, the first impulse of the F signal (which is a marl: ing pulse as shown in Fig. 2) will have been received by the west receiving relay, the armature of which now will be on its marking contact.

Brush SB contacting with segment #1 again completes the operating circuit from the west receiving relay armature, over common ring 13, brush SB and segment #1 of the distributor, through resistances 22 and 23 and the operating windings of the east locking relay ELR and east sencing relay to ground, which cause:- the armatures of these relays to move to their marking positions; and a marking impulse is sent into the loop east. Simultaneously with the closing on segment #1 of this operating circuit the looking circuit for relay WRR is again closed and is main ained during the travel of the brush over segment #1. The 60 milliampere current in this locking circuit is now in a direction so that it opposes the normal 30 milliampere current in the winding, and it is of sufficient strength to overcome the biasing current d hold the armature in marking position in case the loop west should be openec. by g impulse W1 1. the brush traverses segment #1. It will thus be seen that an impulse of the correct polarity necessarily must be sent from the west receiving relay WRR, through the east locking and sending relays ELF. and ESE, because the receiving relay armature is securely locked on its contact during the time the brush SE is contacting with sending segment #1.

The next impulse of the fF signal, the #2 impulse, is an open or spacing impulse. Since the locking circuit for relay WRR is opened when the brush SB leaves segment #1, the relay will presently be under the control of the normal biasing current flowing from positive battery at the marking contact of the west locking relay WLR through resistance 13. There being no current in the line winding of relay WRR at this time, the armature is moved to its spacing contact by the normal 30 milliampere current from the abovesource through itsbiasing winding. The east locking and sending relays ELR and ESR remain on their marking contacts, however, since they are being held by the 30 milliampere current in their locking windings, their operating windings being opened at this time at the segments of the distributor. When the brush SB contacts with the #2 segment, it once again completes the locking circuit from the armature of the west receiving relay WRR through its locking winding. In the same way as previously described, the sending brush SB in passing over the segment #2 causes the operation of the relays ELR and ESR to their spacing contacts and their locking in that position to transmit a spacing signal out over the loop east, and also causes the reversal of the current in the biasing winding on relay ERR; to hold this relay in its marking position during the opening of the loop east.

It has been assumed heretofore that the impulses were received undistorted or substantially as they were transmitted, as shown in Fig. 2.

'It will now be assumed for purposes of illustration that the #3 and #4 impulses are distorted when they are received over the loop west. For instance, referring to Fig. 3 assume that nearly 50% of the first part of the #3 impulse has been wiped out and that nearly50% of the lat er part of the #4 impulse has also been eliminated, possibly by some fortuitous interference on the lines. Thus, instead of a marking impulse extending from time D to time F as shown in Fig. 2, there will be a much shorter marking impulse,- as shown in Fig. 3 which begins a little earlier than half way between times D and E and ends only a little later than half way between times E and F;

It is noted here, that the distributor face is oriented with respect to the incoming signals so that the brush SB just contacts with the edge of a segment when the exact center of an undistorted incoming impulse would be received. Thus the front edge of the #1 segment is on a line with the center of the impulse received between times B and C. Therefore, the west receiving relay armature will be moved to, its marking contact by the incoming distorted #3 impulse just before the brush contacts with the #3 segment and immediately upon reaching this segment the locking circuit through the upper winding of relay WRR is closed simultaneously with the operating circuit for relays ELR and ESE, so that the #3 impulse will be correctly repeated into the loop east.

The #4 impulse (which is also marking as shown in Fig. 2) is next received through the operating winding of the receiving relay WRR. As stated above, it is being assumed that nearly 50% of the latter part of the #4 impulse has been cutoff by distortion as shown in Fig. 3, but the brush SB makes contact with the #4 segmentjust before the current in the loop west goes to Zero. The west receiving relay armature,.therefore, remains locked on its marking contact in spite of the distortion, since the locking circuit through the upper winding of the receiving relay WRR is completed by the brush closing on segment #4 before the receiving relay armature would have moved from its marking contact. Therefore current of the correct polarity is applied to the operating windings of the east locking and sending relays ELR and ESE when the brush SB makes contact with the #4 sending segment. Because the locking time for relay WRR. is equal to the time in which the brush passes the'segment and is made sufiicient, by the proper width of the segment, to fully insure operation of relays ELR and ESR, a premature change in the signal current in loop west, due to distortion, will not interfere with the proper operation of relays ELR and ESR, as long as the distortion is less than 50%. Also, since relays ELR and ESR lock in their operated position before the brush leaves the segment, relay WRR is left free to respond to the next impulse as soon as the brush goes off the segment.

The #5 and #6 impulses are assumed to be per- 3 feet signals and they'will be repeated in a normal way, as were the #1 and #2 impulses.

The #6 impulse is always a marking impulse and is used to stop the brush and set the relays in their normal position in preparation forthe repeating' of the next signal series. The armature of the west receiving relay. WRR is moved to its Reversing direction of transmission Heretofore it has been assumed that the loop cast was closed at the distant station through a source of current applying about 60 milliamperes through the loop to the, upper or operating winding of the east receiving relay ERR. This is the normal condition at thedistant station while it is receiving. If, whilereceiving, the distant operator should wish to signalthe sending station, he would open the loop east fora short interval. Opening of the loop east deenergizes the upper winding of the eastreceiving relay ERR, leaving the relay under the control of its biasing winding. As soon as a marking impulse places relay ELR in marking position, the normal biasing current of 39 milliainperes from the marking contact of the east locking relay ELR, through the high resist-. anee 27 and the biasing winding of relay ERR to V ground. moves the armature of relay ERR to its spacing contact. Thiscompletes a'circuit from ne ative battery over. the spacing contact and armature of the'east receiving relay ERR, over the common ring, brush, stop segment and start magnet of the east to west distributor to positive battery at the armature and marking contact of the west locking relay WLR, and operates the start magnet on the east to west distributor in the same manner as described in detail'abovc for The magnet therefore will, not

the west to east distributor. The east to west distributor brush then moves over its associated segments and, since the loop east remains open, transfers cnly spacing impulses to the west sending relay WSR and west locking relay WLR which operate and hold their armatures in spacing posi tion, thereby keeping the loop west open and biasing relay WRR to marking; relays WSR and VILR consequently will be operated to marking, lock and keep the loop east closed. After completing one revolution the east to West distributor brush stops, because both sides of the start magnet are connected to negative battery, at the spacing contacts of relays WLR and ERR, respectively. When the west operator observes that the loop west has been opened, he knows that the east operator wishes to transmit to him and he closes the loop west through his receiving apparatus. Transmission of signals from the loop east to the loop west throughthe east to'west distributor can then take place in the same manner as described in detail above in connection with transmission through the west to east distributor.

Summary The functions of the different elements of the system be briefly set forth as follows:

Each receiving relay responds to line signals received from its'associated loop and repeats them through the sending segments of the associated distributor to the sending relay in the opposite loop. The biasing winding receives current in either position of the armature in such a direction that it will exert a locking force upon the armature which consequently will be aiding the force by which the armature was operated. Contact chatter is thereby curtailed and the armature is held against operation by a reversed force until the locking winding is deenergiaed.

The function of the sending relays is selfevident. 1 I

' Each locking relay moves in unison with the associated sending relay and supplies current of the requisite polarity to lock the sending relay firmly on one contact or the other, when the operating winding of the sending relay is not energized. It also controls the polarity of the potential applied to one end of the start magnet circuit and thus prevents the brush arm from revolving continuously during a break or open Signal. A third function is to control the polarity of the biasing current in the receiving relay to hold the armature against its marking contact when a spacing signal is transmitted from the corresponding sending relay.

The function of each distributor is to furnish in its stop position a path for the start impulse from the armature of theassociated receiving relay to the start magnet, and thereafter, during the transferring of signals, to temporarily lock the receiving relay at the center of each received signal impulse to prevent distortion in the incoming signals from being retransmitted. A second function is-to permit the associated receiving relay to control the opposite sending relay only. while the receiving relay is locked in position by the distributor, and to limit this control time to be only sufilcient for the certain locking of the. opposite sending relay in its new position, thus reducing the locking time for the receiving relay to a minimum and providing maximum time for the receiving relay to respond to incoming signals.

The use of but a single set of interrupter contacts for timing of the impulse transfer from the receiving circuit to. the retransmitting circuit particularly adapts this system for use with timing devices of many and varied types, the principal requirements of such a device being a set of oiT-normal contacts closed in the stop position and a set of interrupter contacts operated in off-stop positions by a motor driven member in its travel from one stop position to the next upon the release of the member in response to the start impulse. Thus the start-stop interrupter disclosed by M. P. Chaplin in Patent No. 1,540,313, issued June 2, 1925 may readily be adapted for use in the present system.

It is within the scope of the invention to insert circuits or networks in the various relay operating circuits for the purpose of speeding up or timing operations at any point in the system; such an arrangement is shown for the sake of illustration as a condenser and resistance network N partly in multiple and partly in series relation to the start magnet, effective in accordance with known principles in overcoming the retarding efiects of the inductance associated with the start circuit and thus insuring a quick start of the distributor; a condenser 24 is also shown in the operating circuit for relays ELR and ESR and serves to improve the wave shape oi the operating current and thus to quicken the operation of these relays; networks may also be inserted for the reduction of sparks at relay and distributor contacts Without departing from the spirit of the invention.

The invention furthermore is not limited to regenerative repeaters for use in start-stop systems employing the 7 unit code, but is readily adapted to any other uniform start-stop code.

What is claimed is:

l. A regenerative impulse repeater comprising receiving relay means, sending relay means, a single set of interrupter contacts motor driven in synchronism with incoming impulses, an intermittently energized transfer circuit for operation of said sending relay means by said receiving relay means, and an intermittently energized circuit for self-locking of said receiving relay means, said two circuits being connected in multiple through said set of contacts for concurrent intermittent energization of them.

2. A regenerative start-stop telegraph signal repeater comprising receiving relay means having contacts and locking winding, sending relay means having self-locking winding and contact means, start-stop distributing means having a start magnet and a single set of interrupter contacts for transfer of impulses between said re-- ceiving and sending relay means in isochronism with incoming impulses, a substantially distortionless impulse supply circuit from contacts of said receiving relay means to said set of contacts, start circuit means for said start magnets connected through said set of contacts to said supply circuit in stop position of said distributing means, operating circuit means for said sending relay means intermittently connected through said set of contacts to said supply circuit, and a locking circuit for the locking winding of said receiving relay means intermittently connected through said set of contacts to said supply circuit.

3. A start-stop regenerative telegraph repeater comprising receiving relay means including a locking winding and contacts; distributor mechanism having a single set of circuit interrupting contacts operated in isochronism with received impulses and having a start magnet and a stop position; a distortionless start circuit for said magnet completed in said stop position to contacts of said receiving relay means; retransmitting relay means including winding and contacts for self-locking between impulses from said receiving relay means, impulse transfer circuit means for operation of said retransmitting relay means and locking circuit means for the loci-:- ing winding of said receiving relay means, both of said circuit means being connected through said set of contacts to be open in said stop position and to be concurrently and intermittently energized in off-stop positions of said mechanism from contacts on said receiving relay means.

4. A start-stop regenerative telegraph repeater connected between a west line circuit and an east line circuit, including east-west equipment for retransmission from said east line to said west line and corresponding west-east equipment; said east-west equipment comprising receiving relay means having an operating winding in said east line, locking winding and contacts; sending relay means having contacts in said west line, winding and contacts for self-locking between its operations; distributing mechanism for the timing of relay operations in isochronism with receivedsignal impulses and having a single set of circuit interrupting contacts, a start magnet and a stop position; a distortionless start circuit completed to contacts on said receiving relay means for. operation of said magnet in stop position only; an operating circuit for said sending relay means intermittently completed through said set of contacts in off-stop positions to contacts on said receiving relay means for transfer of impulses; a locking circuit for the locking winding of said receiving relay means open in said stop position and intermittently completed through said set of contacts in ofistop positions for self-locking of said receiving relay means during the transfer of individual impulses; and a holding circuit from the looking contacts of the sending relay means in said west-east equipment for the locking winding of said east-west receiving relay means in'said stop position during transmission through said west-east equipment.

THOMAS A. MCCANN. 

